The rally in downtown Tehran featured the sort of thumping, Turkish-style dance music that is normally banned in the Islamic republic but has become increasing popular at hardliner events.

It is made acceptable to conservative ears with the addition of lyrics such as "the US is a murderer" and "Palestinian mothers are losing their children" and, of course, the ubiquitous "Death to America".

Participants blamed the middling turnout on rushed preparations.

"The publicity was a bit weak. I only learned about today's demo around midnight, and I'm coming directly from the hospital because I'm a medical student," said Ali Esfahani, 23.

He said Trump's decision to move the American embassy to Jerusalem, which was widely condemned across the globe, "was one more cruelty on top of America's previous oppressions" and could not be tolerated.

Such protests tread a fine line, pledging support for the Palestinian cause without calling for direct military action by Iran.

"I don't think there will be a need to send any troops because there are a lot of people in Lebanon, Syria and inside the Palestinian territories. They will be enough to get rid of the Israelis," a cleric, Seyed Abdullah Hosseini, told AFP.

A neon board on the side of the square announced that there were only 8,240 days left for Israel -- a reference to a speech by supreme leader Ayatollah Ali Khamenei in which he predicted the end of Israel by 2030.

"Mr Trump has done a good job of speeding things up. We were expecting Israel to be dismantled later... but this is the beginning of the end of Israel," said Hosseini.

"We have to thank him for what he did."

Later in the day, President Hassan Rouhani told the Palestinian Islamist movement Hamas's leader in Gaza on the phone that together Muslims could defeat Israel.

"The oppressed people of Palestine and Islamic ummah (community) will undoubtedly defeat the US-Israeli plan with their unity and resistance," Rouhani told Ismail Haniya, as quoted by the government's website.